The present invention pertains generally to metal working and particularly to electrodes for underwater, wet, electric-arc welding and oxyarc and arcair cutting.
The two principal operations in underwater metal working are welding and cutting. An electric-arc welder operates by establishing a confined arc between the work-piece and an electrode. Heat is generated by the arc and causes a molten pool in the surface of the work-piece and a melting of the electrode. As the electrode melts, metal is transferred from the electrode to the metal surface. The weld is formed when the molten metal solidifies upon cooling.
Generally, it is necessary to coat the electrode with flux in order to obtain a high-quality weld. Examples of chemical compounds used as fluxes are calcium silicate, iron silicate, ferrosilicon, titanium oxide, ferromanganese, and calcium fluoride. In a water environment, additional measures must be taken on account of the cooling effect of the water, hydrogen entrapment in the weld, electrical losses through the water, and destruction of the flux coating by water absorption.
Since oxyarc and arcair cutting processes are similar to electric-arc welding in that these processes utilize an electric arc between a work-piece and an electrode, these processes also experience serious problems in a water environment. The cooling effect of the water slows down the cutting and roughens the finish of the cut. The electrical losses through the water interfere with the control of the cutting.
Various techniques are employed to overcome these problems. One technique is to isolate the area to be worked from the water by a dry water-tight chamber which can be large enough to contain a man or just large enough for the metal-working tool. The main disadvantages with this technique are cost, slowness, and a limited application.
The technique showing the greatest potential is metal-working in a water environment with coated electrodes. These electrodes are prepared by coating the electrodes with a water-impervious material such as cellulose lacquer or polyvinyl chloride. The presently used materials and methods of applying the coating produce electrodes with numerous shortcomings. The electrodes are not sufficiently waterproofed on account of the porosity of material arising from its nature or the method of application and because of a poor seal between the coating and the electrode. Another defect is poor electrical insulation. Some of the coatings are applied too thickly or are made from materials which do not completely burn. Consequently, the coating interferes with the performance of the tool. Another defect inherent with some materials is that oxidation products thereof enter the welding puddle. Presently, electrodes cannot be easily waterproofed near the working area and so storage problems are encountered. Compounding this difficulty is the poor shelf-life of most waterproofed electrodes.